I've had a decent experience with Grizzly's customer service.
As for the difference between a parallelogram and older style jointers, I've stolen the following from lumberjocks.com
"A wedge designed jointer has the cutterhead section shaped like a pyramid, with the tables attached via dovetail ways.
The tables move up or down by being forced along the side of the pyramid by screws.
A parallelogram jointer has the beds attached to the head via arms that pivot. The parallelogram shape is changed by screws to move the beds up or down.
The older wedge type jointers are just fine, as any 100 year old machine will atest to. Dovetailed ways last a long time, and are shimmed for jointer alignment.
A well made parallelogram would work well, as long as it has large bearing surfaces, with dissimilar metals with oil for lubrication. Otherwise if it has small bearing areas it will wear and become loose.
In another 80 years, we’ll have good experience with the life of these machines.
As with all machines, quality means precision which means money, and a jointer is no exception, you’ll get what you pay for with either design."
HT to NBeener, lumberjocks.com